VRO electrical question

[ChrisQ]

trying to locate a short that is killing my tach signal and charging current from my regulator/rectifier and, by running the direct tach test by taking the yellow/grey wire from the charge coil directly to the grey tach sender I found no signal....It is being loaded down by an apparant short in the VRO.
I have 1.5K ohms between the grey wire and the black going into the VRO 4-wire harness. While not a direct short, if I disconnect the VRO the tach signal is good, as soon as I reconnect the VRO, I lose signal on the tach line.
My question is, shouldn't the resistance between the grey and black wire of the VRO be very near infinite?
Second, do I have a bad VRO?
Thanks,
Chris

 

[HighTrim]

Re: VRO electrical question

When the rectifier goes, all kinds of weird things can happen.

Have you tested the rectifier? Check out Joe Reeves thread in the FAQ here on iboats for his testing procedures and let us know what you find.

 

[ChrisQ]

Re: VRO electrical question

Thanks for the reply, but let me clarify that I already did exactly what Joe said, but he left out a third variable and that was my question. Joe says to connect the yellow/grey wire from the charge coil to the grey tach sender and if that works then your rectifier/regulator is bad... If that does not work then the tach is bad. In my case, the tach does not work UNTIL I disconnect the VRO. When I disconnect the VRO the tach works fine, when I connect the VRO plug again, it kills the tach. Leads me to believe there is a VRO problem. I have only run the motor less than a minute to test it like this (running on residual oil only) I am going to make up a a tank of premix tonight so I can run it longer.
Any input would be appreciated

 

[Chris1956]

Re: VRO electrical question

Chris, Whereas you may have found the culprit (VRO), be aware that the purple wire, grey wire and others run to places in my '98 Johnny, that are unexpected, and this makes the wiring diagram more complicated that expected. For example, you could have a bare wire in the boat harness, and when you plug in the VRO conector, a splice is made from the grey to the boat harness, which kills the singal.

Do you have a wiring diagram for your exact motor? If not, you need to get one, before you go replacing things.

 

[ChrisQ]

Re: VRO electrical question

Thanks for the reply...
Good point and YES I am aware of the wire harness issues. I am doing a total overhaul of a '98 Aquasport Osprey and have pulled everything out and removed the console... put new gauges, terminal blocks, etc... I have the "other" purple,grey, black harness that you refer to hanging free and that is actually where I am checking the signals when the tach harness plug is connected.
I am hesitant to remove (as opposed to replacing) the VRO even though I have located the problem in the electronics module. I am curious, is this a common problem with '98 evinrude V4 looper VRO's? The reason I ask, I have located two different used VRO's on Ebay and had the owners take ohm readings across the grey and black wires going into the VRO harness. BOTH have between 2-5 ohms across them... Might as well call it continuity. Either of those would produce the same problem I am having as it would shunt the tach signal to ground. So now I am really confused? Can anyone tell me what that ohm reading should be? Maybe read a new one or unplug the harness from your working VRO and read across the grey and black wires.
Thanks

 

[Chris1956]

Re: VRO electrical question

The OEM Service Manual I have for the '98 V4 and V6s have a troubleshooting guide for the VRO (Actually called an OMS) Circuit board. You might get a manual and go thru it. You can also replace just the OMS circuit board on that motor.